Geology of Cornwall

The geology of Cornwall, England, is dominated by its granite backbone, part of the Cornubian batholith, formed during the Variscan orogeny. Around this is an extensive metamorphic aureole (known locally as killas) formed in the mainly Devonian slates that make up most of the rest of the county. There is an area of sandstone and shale of Carboniferous age in the north east, and the Lizard peninsula is formed of a rare section of uplifted oceanic crust.

Cornwall forms the tip of the south-west peninsula of the island Great Britain, and is therefore exposed to the full force of the prevailing winds that blow in from the Atlantic Ocean. The coastline is composed mainly of resistant rocks that give rise in many places to impressive cliffs.

The north and south coasts have different characteristics. The north coast is more exposed and therefore has a wilder nature. The prosaically-named High Cliff, between Boscastle and St Gennys, is the highest sheer-drop cliff in Cornwall at 735 ft (224 m). However, there are also many extensive stretches of fine golden sand which form the beaches that are so important to the tourist industry, such as those at St Ives, Hayle, Perranporth and Newquay. The only river estuary of any size on the north coast is that of the Camel, which provides Padstow with a safe harbour.

The south coast, dubbed the riviera, is somewhat more sheltered and there are several broad estuaries formed by drowned valleys or rias that offer safe anchorages to seafarers, such as at Falmouth and Fowey. Beaches on the south coast usually consist of coarser sand and shingle, interspersed with rocky sections of wave-cut platform.

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